1. Field
The present invention relates to aircraft components. More particularly, the present invention relates to vacuum assisted resin transfer molding with a reusable vacuum bag.
2. Related Art
Vacuum assisted resin transfer molding (VARTM) is a composite manufacturing process in which dry fibers of composite material are laid on a tool beneath a nylon vacuum bag and vacuum sealed while liquid resin is drawn through the composite material with a vacuum pump. Traditionally, a flow media or resin distribution media made of a nylon, plastic, or metal and having a high permeability is placed over the composite material to allow resin to flow over it and subsequently be evenly dispersed throughout the composite material. Additionally, a breather cloth made of fiberglass or peel-ply may be placed beneath the nylon vacuum bag to help pull resin through the material and allow air to be evacuated from between the nylon vacuum bag and the tool. The nylon vacuum bag may then be placed over the composite material, flow media, and breather cloth, and sealed to the tool with chromate vacuum bag tape. A vacuum inlet and a vacuum outlet may allow the liquid resin to be pulled through the composite material. Once the liquid resin is distributed throughout the composite material and the vacuum bag is compressed against the composite material by vacuum force, the vacuum pump may be removed, and the part may then be cured by heat to harden the composite part.
Some disadvantages to the VARTM method include the need to individually cut the flow media, breather cloth, and vacuum bag for placement over the composite material, particularly when manufacturing complex-shaped composite parts. This may be time consuming and error-prone. Additionally, with complex-shaped composite parts, the flow media may need to be heat-set or spliced into many pieces to allow the flow media to conform to the desired shape for resin distribution. And, because the flow media, breather cloth, and vacuum bag are separate parts laid together, they may unintentionally move or shift during the vacuum and curing process.
Another disadvantage to the traditional VARTM method is that the vacuum bag, flow media, and breather cloth are not reusable. As the liquid resin is dispersed throughout the composite part, it also permeates the vacuum bag, flow media, and breather cloth, so that during the curing process, these items are also hardened as a result. Therefore, even when manufacturing identical parts, a new vacuum bag, flow media, and breather cloth must be used in the production of each individual part.
Finally, in the traditional VARTM process, once the vacuum pump is removed, the vacuum bag tape often leaks or bleeds off vacuum, and the vacuum bag therefore loses vacuum integrity when the vacuum source is turned off or disconnected. This, in turn, may negatively impact the structural integrity of the resulting part.
Therefore an improved apparatus and method for forming composite parts through vacuum assisted resin transfer molding is desired.